Birds of a Great Basin sagebrush habitat in east-central Nevada

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' United States
i2 Department
^ cjf Agriculture

Forest Service

Intermountain
Research Station

Research Paper
INT-452

April 1992

Birds of a Great Basin
Sagebrush Habitat in
East-Central Nevada

Dean E. Medin

THE AUTHOR

RESEARCH SUMMARY

DEAN E. MEDIN recently retired as a research wildlife
biologist with the Intermountain Research Station at
the Forestry Sciences Laboratory in Boise, ID. He
earned a B.S. degree in forest nnanagement from Iowa
State University in 1957, and from Colorado State
University he earned an M.S. degree in wildlife man-
agement in 1959 and a Ph.D. degree in range ecosys-
tems in 1976. His research has included studies in
mule deer ecology, big-game range improvement,
mule deer population modeling, and nongame bird and
small mammal ecology and habitat management.

ACKNOWLEDGMENTS

I gratefully acknowledge the valuable field assis-
tance of J. Russell Groves and Michael D. Carter.
Jean Martin, illustrator, drew the cover art.

Breeding bird densities and bird community organi-
zation of a Great Basin sagebrush ecosystem in the
Snake Valley of east-central Nevada were determined
by spot-mapping on a 20-ha plot during April, May,
and June, 1981 to 1983. Total density of the breeding
bird community ranged from 3.35 to 3.48 individuals/ha
over the 3-year study. Bird standing crop biomass
ranged from 53 to 61 g/ha. From five to six species
bred on the study plot each year. The most abundant
birds were Brewer's sparrows and sage sparrows.
Those two species, plus the sage thrasher and black-
throated sparrow, characterized the breeding bird
community and accounted for over 95 percent of the
total population. Horned larks and western meadow-
larks were less common. Results are compared with
breeding bird populations in Great Basin sagebrush
habitats elsewhere in the United States.

Intermountain Research Station
324 25th Street
Ogden, UT 84404

Birds of a Great Basin Sagebrusli
Habitat in East-Central Nevada

Dean E. Medin

INTRODUCTION

Kiichler (1970) mapped the Great Basin sage-
brush (Artemisia) ecosystem type in North America.
The type covers nearly 18 milHon ha and extends
over parts of Nevada, Utah, Arizona, Colorado,
California, and New Mexico. West (1983) defined
the ecosystem type and described its features. The
ecosystem type is located south of the sagebrush
steppes and generally north of the creosotebush
(Larrea) and blackbrush (Coleogyne) types. It is
elevationally positioned between the salt-desert
shrublands at the lowest elevations and the conifer
woodlands on the lower flanks of the mountains
(West4983).

There are few quantitative assessments of breed-
ing bird populations in these vast areas used
primarily for domestic livestock production. This
information is basic to understanding the ecology
of semidesert birds and the stewardship of their
habitats. In this paper I describe breeding bird
densities of a sagebrush ecosystem in the Snake
Valley of east-central Nevada and compare them
with other quantitative studies of birds in similar
Great Basin sagebrush habitats. The study, con-
ducted from 1981 to 1983, was restricted to pas-
serine species.

STUDY AREA

The study area, located 68 km southeast of Ely in
southeastern White Pine County, NV, has a median
elevation of approximately 1,710 m. The study site
is generally flat and positioned on a broad, gently
sloping pediment facing northeast. The area is
bounded on the west by foothills and mountains
and on the east by a flat valley bottom. There are
no seeps, springs, or live streams on the site. Dry
washes are a prominent feature of the local land-
scape. The area is semiarid with cold winters and
hot, dry summers. Maximum temperatures in
summer may exceed 35 °C, and minimum tempera-
tures in winter often drop to -29 °C (Houghton and
others 1975). Average annual precipitation at Ely
(elevation 1,905 m) is 221 mm, with peaks in April
and May (U.S. Department of Commerce 1970).

During the study period, Wyoming big sagebrush
(Artemisia tridentata var. wyomingensis) dominated

the vegetation. Other important shrubs included
black sagebrush (A. arbuscula var. nova), rabbit-
brush (Chrysothamnus uiscidiflorus), and spiny hop-
sage (Grayia spinosa). The principal herbaceous
species were grasses, especially cheatgrass (Bromus
tectorum), and Sandberg bluegrass (Poa sandbergii).
Forbs were less abundant, but species of milkvetch
(Astragalus), fleabane (Erigeron), and pepperweed
(Lepidium) were widespread.

The study area was grazed lightly by domestic
sheep trailing to and from seasonal ranges. The
study site is on public lands and administered by
the Bureau of Land Management, U.S. Department
of the Interior.

METHODS

A 20-ha plot was censused for breeding birds
using the Williams spot-map method (International
Bird Census Committee 1970). The census plot was
chosen to best represent the Great Basin sagebrush
ecosystem type in the Snake Valley. The square
plot was surveyed and gridded with points num-
bered and marked with stakes at 75-m intervals.
Ten census visits to the plot were made annually
between April 1 and June 12, from 1981 to 1983.
Most of the spot-mapping was done between sunrise
and early afternoon when birds were most active.
To ensure complete coverage, the plot was censused
by walking within 50 m of all points on the grid.
Census routes were varied. Recorded bird observa-
tions extended a minimum of 50 m beyond plot
boundaries.

At the end of the sampling period each year,
clusters of observations and coded activity patterns
on species maps were circled to define breeding bird
territories. Fractional parts of boundary territories
were included in the results. The reciprocal of
Simpson's index (Z) = 1/ Z p.^, where p. is the propor-
tion of the sample belonging to the ith species) was
used to calculate species diversity (Hill 1973). Bird
standing crop biomass was calculated as B = L
(N.W.), where N. is the density of the ith species,
and W. is the mean body weight (g) per individual
of the ith species. Species weights were from
Dunning (1984).

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Plant taxonomy follows Holmgren and Reveal
(1966). Bird nomenclature is from the American
Ornithologists' Union (1983) checklist.

RESULTS AND DISCUSSION

Six passerine bird species bred on the study plot
(table 1). Total breeding bird density ranged from
3.35 to 3.48 individuals/ha over the 3-year study.
Total bird standing crop biomass ranged from 53
to 61 g/ha. Five to six species were territorial on the
plot in any given year. The most common breeders
were Brewer's sparrows (Spizella breweri) and sage
sparrows {Amphispiza belli). Those two species,
plus the black-throated sparrow {Amphispiza
bilineata) and sage thrasher {Oreoscoptes mon-
tanus), accounted for over 95 percent of the total
passerine population. Horned larks (Eremophila
alpestris) and western meadowlarks {Sturnella
neglecta) were less common.

Other species, observed as occasional visitors on
or over the study plot during the breeding season,
included northern harrier {Circus cyaneus), red-
tailed hawk {Buteo Jamaicensis), golden eagle {Aquila
chrysaetos), American kestrel {Falco sparverius),
sage grouse {Centrocercus urophasianus), mourning
dove {Zenaida macroura), broad-tailed humming-
bird {Selasphorus platycercus), violet-green swallow

{Tachycineta thalassina), American crow {Corvus
brachyrhynchos), common raven {Corvus corax), and
loggerhead shrike {Lanius ludovicianus).

Less frequently observed birds were ferruginous
hawk {Buteo regalis), prairie falcon {Falco mexi-
canus), common nighthawk {Chordeiles minor), cliff
swallow {Hirundo pyrrhonota), barn swallow {Hirundo
rustica), black-billed magpie {Pica pica), mountain
bluebird {Sialia currucoides), green-tailed towhee
{Pipilo chlorurus), and vesper sparrow {Pooecetes
gramineus).

Brewer's sparrows, sage sparrows, and sage
thrashers — widespread species in Great Basin sage-
brush ecosystems — occurred throughout the study
plot. Braun and others (1976) referred to those
species as sagebrush obligates because of their close
association with sagebrush habitats. In my study,
those species were observed most often where sage-
brush shrubs were taller and more dense. Sage
sparrows and sage thrashers have been found to be
more abundant in areas of high sagebrush densities
(Wiens and Rotenberry 1981). Horned larks and
western meadowlarks were found in more restricted
locations on the study plot where shrub vegetation
was lower and more open. Although black-throated
sparrows were distributed throughout the plot, I
was unable to discern any association with the
structure or composition of the vegetation except

Table 1 — Passerine breeding bird densities (individuals/ha) in Great Basin sagebrush vegetation, east-central
Nevada, 1981-1983

Foraging

Nesting

Density

Species

category'

substrate^

1981

1982

1983

Horned lark

GGO

G

0.15

0.15

0.12

{Eremophila aipestris)

Sage thrasher

GGI

B

.40

.12

.28

{Oreoscoptes montanus)

Brewer's sparrow

GGI

B

1.68

1.52

1.50

{Spizella brewer!)

Black-throated sparrow

CGI

B

.35

.80

.48

{Amphispiza bilineata)

Sage sparrow

GFO

B

.90

.85

.95

{Amphispiza belli)

Western meadowlark

GGI

G

+

.02

{Sturnella neglecta)

Total individuals/ha

3.48

3.44

3.35

Standing crop biomass (g/ha]

61

53

58

Species richness (S)

5

5

6

Species diversity (D)^

3.08

3.19

3.23

Species evenness (E)^

.82

.87

.83

'After DeGraff and others (1985). GGO = ground gleaning omnivore; GGI

= ground gleaning insectlvore; CGI

= canopy

gleaning insectivore; GFO = ground foraging omnivore.
^G = ground nester: B = bush nester.

2+ indicates bird observed infrequently (less than three registrations).
■•Species weights from Dunning (1984).
^After Hill (1973).

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that the tallest shrubs were used as singing
perches.

Brewer's sparrow, the most abundant breeder in
my study, is probably the most characteristic bird
of sagebrush-dominated ecosystems throughout
western North America (Ryser 1985; Wiens and
Rotenberry 1981). They are dependent on shrubby
habitats that provide protective cover, song perches,
and nest sites (Johnsgard and Rickard 1957). This
sparrow normally breeds in sagebrush habitats but
will also nest in a variety of other suitable shrubs
(Short 1984). Effective sagebrush control reduces
habitat use by the Brewer's sparrow (Best 1972).
The abundance of this sparrow in its breeding range
has been shown to be positively correlated with
percentage cover of shrubs and cacti, forbs, and bare
ground, and negatively correlated with percentage
cover of grasses and litter (Rotenberry and Wiens
1980a).

Sage sparrows and sage thrashers are frequently
cohabitants in sagebrush ecosystems over much of
their breeding range (Wiens and Rotenberry 1981).
Sage sparrows were singing sporadically when I
began census work on April 1; sage thrashers were
first recorded singing about 1 to 2 weeks later.
Their breeding territories were distributed through-
out the study plot, and they frequently overlapped.
I found both species most abundant in areas with
high sagebrush densities. They apparently prefer
larger shrubs for nesting (Peterson and Best 1985;
Reynolds 1981). McAdoo and others (1989) found
sage thrasher abundance uncorrelated with shrub
height.

Black-throated sparrows are locally common
breeders in Great Basin sagebrush ecosystems
(Ryser 1985). They also occur in a variety of other
shrubby habitats, particularly those of drier, hotter.

desert valleys (DeGraaf and others 1991). Their
breeding range extends farther south than that of
Brewer's sparrows, sage sparrows, and sage thrash-
ers (American Ornithologists' Union 1983). I found
their breeding territories widespread on the study
plot and generally noncontiguous. Singing males
were first noted in mid-April, and pairing was
evident by early May. Breeding density in 1982
was about twice that in 1981 and 1983 (table 1).

Horned larks and western meadowlarks are
widely distributed species and among the most
adaptable birds of Western rangelands (DeGraaf
and others 1991). They are common permanent
residents in the Great Basin (Ryser 1985), and
generally categorized as grass-inhabiting species
(Rotenberry and Wiens 1980b). I found them
localized on the study plot and in consistently low
densities (table 1). Among the breeding bird species
recorded during the study, only the horned lark and
western meadowlark were ground nesters.

Few other assessments of breeding bird densities
in the Great Basin sagebrush ecosystem type are
available (table 2). McKernan (1978a, b) and Stewart
(1979a, b) reported total breeding bird densities of
0.38 to 2.30 individuals/ha on two sagebrush study
plots in east-central California. One plot was heavi-
ly grazed by feral burros and the other was an un-
grazed control. Increased density on the heavily
grazed plot in 1979 may have been related to a tem-
porary reduction of grazing in that year. Castrale
(1982) found total densities on variously treated
sagebrush plots in north-central Utah ranging from
1.62 to 2.18 individuals/ha. Breeding birds included
Brewer's sparrow, sage thrasher, vesper sparrow,
horned lark, and western meadowlark.

Although not included in the Great Basin sage-
brush ecosystem type, breeding bird densities

Table 2 — Breeding bird densities (individuals/ha) in the Great Basin sagebrush ecosystem type''

Total Number of

Location

Year

density

species

Treatment

Reference

East-central California

1978

0.38

3

Heavily grazed

McKernan 1978a

1978

.76

5

Ungrazed

McKernan 1978b

East-central California

1979

2.30

6

Heavily grazed

Stewart 1979a

1979

.86

6

Ungrazed

Stewart 1979b

North-central Utah

1979

2.00

5

1 7-year-old plowed

Castrale 1982

1980

2.18

5

1 7-year-old plowed

Castrale 1982

North-central Utah

1979

1.62

4

4-year-old chained

Castrale 1982

1980

1.82

5

4-year-old chained

Castrale 1982

North-central Utah

1979

2.12

5

4-year-old burned

Castrale 1982

1980

1.82

6

4-year-old burned

Castrale 1982

East-central Nevada

1981

3.48

5

Lightly grazed

This study

1982

3.44

5

Lightly grazed

This study

1983

3.35

6

Lightly grazed

This study

'Great Basin sagebrush ecosystem type as mapped by Kuchler (1970) and defined by West (1983).

reported by Rotenberry and Wiens (1980b) in more
northerly shrubsteppe habitats compared favorably
to those I found in east-central Nevada. Average
total densities reported by those authors from 14
Northwestern shrubsteppe locations ranged from
3.48 to 3.68 individuals/ha from 1977 to 1979. The
most abundant species in their surveys included
Brewer's sparrows, sage sparrows, sage thrashers,
horned larks, and western meadowlarks.

REFERENCES

American Ornithologists' Union. 1983. Checklist of
North American birds. 6th ed. Washington, DC:
American Ornithologists' Union. 877 p.

Best, Louis B. 1972. First-year eflFects of sagebrush
control on two sparrows. Journal of Wildlife
Management. 36(2): 534-544.

Braun, Clait E.; Baker, Maurice F.; Eng, Robert L.;
Gashwiler, Jay S.; Schroeder, Max H. 1976.
Conservation committee report on effects of alter-
ation of sagebrush communities on the associated
avifauna. Wilson Bulletin. 88(1): 165-171.

Castrale, John S. 1982. Effects of two sagebrush
control methods on nongame birds. Journal of
Wildlife Management. 46(4): 945-952.

DeGraaf, Richard M.; Tilghman, Nancy G.; Anderson,
Stanley H. 1985. Foraging guilds of North American
birds. Environmental Management. 9(6): 493-536.

DeGraaf, Richard M.; Scott, Virgil E.; Hamre, R. H.;
Ernst, Liz; Anderson, Stanley H. 1991. Forest and
rangeland birds of the United States. Agric. Handb.
688. Washington, DC: U.S. Department of
Agriculture. 625 p.

Dunning, John B., Jr. 1984. Body weights of 686
species of North American birds. Monogr. 1. Tucson,
AZ: Western Bird Banding Association. 38 p.

Hill, M. 0. 1973. Diversity and evenness: a unifying
notation and its consequences. Ecology. 54(2):
427-432.

Holmgren, Arthur H.; Reveal, James L. 1966. Check-
list of the vascular plants of the Intermountain
Region. Res. Pap. INT-32. Ogden, UT: U.S. Depart-
ment of Agriculture, Forest Service, Intermountain
Forest and Range Experiment Station. 160 p.

Houghton, John G.; Sakamoto, Clarence M.; Gifford,
Richard 0. 1975. Nevada's weather and climate.
Spec. Publ. 2. Reno, NV: University of Nevada,
Nevada Bureau of Mines and Geology. 78 p.

International Bird Census Committee. 1970. An
international standard for a mapping method in
bird census work. Audubon Field Notes. 24(6):
722-726.

Johnsgard, P. A.; Rickard, W. H. 1957. The relation
of spring bird distribution to a vegetation mosaic in
southeastern Washington. Ecology. 38(1): 171-174.
, Kiichler, A. W. 1970. Potential natural vegetation
(map at scale of 1:7,500,000). In: The National Atlas
of the U.S.A. Washington, DC: U.S. Geological
Survey: 90-91.

McAdoo, J. Kent; Longland, William S.; Evans,
Raymond A. 1989. Nongame bird community
responses to sagebrush invasion of crested wheat-
grass seedings. Journal of Wildlife Management.
53(2): 494-502.

McKernan, Robert L. 1978a. Sagebrush scrub I.
American Birds. 32(1): 104.

McKernan, Robert L. 1978b. Sagebrush scrub II.
American Birds. 32(1): 104.

Peterson, Kenneth L.; Best, Louis B. 1985. Nest-site
selection by sage sparrows. Condor. 87(2): 217-221.

Reynolds, Timothy D. 1981. Nesting of the sage
thrasher, sage sparrow, and Brewer's sparrow in
southeastern Idaho. Condor. 83(1): 61-64.

Rotenberry, John T.; Wiens, John A. 1980a. Habitat
structure, patchiness, and avian communities in
North American steppe vegetation: a multivariate
analysis. Ecology. 61(5): 1228-1250.

Rotenberry, John T.; Wiens, John A. 1980b. Temporal
variation in habitat structure and shrubsteppe bird
dynamics. Oecologia. 47: 1-9.

Ryser, Fred A., Jr. 1985. Birds of the Great Basin.
Reno, NV: University of Nevada Press. 605 p.

Short, Henry L. 1984. Habitat suitability index
models: Brewer's sparrow. FWS/OBS-82/10.83.
Washington, DC: U.S. Department of the Interior,
Fish and Wildlife Service, Division of Biological
Services. 16 p.

Stewart, Robert M. 1979a. Sagebrush scrub I.
American Birds. 33(1): 94-95.

Stewart, Robert M. 1979b. Sagebrush scrub II.
American Birds. 33(1): 95.

U.S. Department of Commerce. 1970. Climatological
summary: Ely, Nevada. In: Climatography of the
United States No. 20-26. Reno, NV: Environ-
mental Science Services Administration in
cooperation with University of Nevada, College
of Agriculture. 2 p.

West, N. E. 1983. Great Basin-Colorado Plateau
sagebrush semi-desert. In: West, N. E., ed. Eco-
systems of the world. Vol. 5. Temperate deserts
and semideserts. New York: Elsevier Publishing
Company: 331-349.

Wiens, John A.; Rotenberry, John T. 1981. Habitat
associations and community structure of birds in
shrubsteppe environments. Ecological Monographs.
51(1): 21-41.

4

Medin, Dean E. 1992. Birds of a Great Basin sagebrush habitat in east-central Nevada.
Res. Pap. INT-452. Ogden, UT: U.S. Department of Agriculture, Forest Service, Inter-
mountain Research Station. 4 p.

Breeding bird populations ranged from 3.35 to 3.48 individuals/ha over a 3-ye'ar study
conducted from 1981 to 1983. Brewer's sparrows, sage sparrows, sage thrashers, and
black-throated sparrows were numerically dominant. Horned larks and western meadow-
larks were less common. Results are compared with bird populations in Great Basin
sagebrush habitats elsewhere in the United States.

KEYWORDS: breeding birds, density, diversity, biomass, sagebrush ecosystem type,
Artemisia tridentata, semi-desert

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